This renewal application requests continued support of our post-doctoral training progrann in Pediatric Infectious Diseases. The discipline of Pediatric Infectious Diseases is critically important to promote an increased understanding ofthe pathogenesis and effective treatment of human pathogens in children. During the decade that the training program has been funded, our faculty and trainees have performed basic, translational, and clinical research in host-pathogen interactions; virulence factors; emerging pathogens; molecular epidemiology; antimicrobial resistance and the appropriate use of antimicrobial agents and adjuvant therapies; and the development, safety and efficacy of vaccines. The goal of our program continues to be the development of physician investigators who seek careers in Pediatric Infectious Diseases and train them in basic, translational, and/ or clinical research. During the past decade, we have successfully trained 9 fellows all of whom are engaged in academic endeavors and currently have 3 trainees. The Pediatric Infectious Diseases faculty has expanded to 9 physicians all of whom are engaged in research. Our training program is increasingly interdisciplinary thanks to the enormous academic resources available at Columbia University Medical Center and now includes key faculty from the Departments of Medicine, Microbiology, and Cell Biology, as well as the Schools of Nursing and Public Health. As a result of these strengths and the availability of the training program, we continue to recruit top applicants who have completed their pediatric residency and general pediatric clinical training and seek to develop both their research skills and clinical skills in Pediatric Infectious Diseases. The training program in pediatric infectious diseases lasts for 3 years. We recruit one trainee per year. We are requesting 5 more years of support to fund 3 post-doctoral trainees each year, i.e. a 1^', 2*^ and 3^^^ year trainee. During the training program, the trainees engage in scholarly research with a Core-trainer from Pediatric Infectious Diseases and, if applicable, co-mentors from other disciplines. The trainees also acquire clinical expertise in Pediatric Infectious Diseases and are eligible to be board certified in this discipline at the completion of their training. RELEVANCE (See instructions): Physicians trained in Pediatric Infectious Diseases help to care for incredibly diverse patients including otherwise healthy children who contract a serious infection; children and adolescents living with chronic illnesses such as HIV/AIDS, cystic fibrosis, and congenital heart disease; premature infants; and children undergoing transplantation or chemotherapy for malignancies. Our discipline helps to address immigrants' unique medical issues and the publics' concerns about vaccine safety and antibiotic resistance.